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Y v I A sept. 1s, 192s;- F KOLSTE? ET L Re. 17,086

ELECTROMAGNETIC SOUND BEPRODUCER 1 t e e. vu-w s t e e. h s 2 original Filed Jan.' 18, 1927 sept. 18,1928. F- KOLSTER ET ^L Re. 17,086

ELECTROMAGNETIC SOUND REPRODUCER 2 sheets-sheet 2 original Filed Jan. 13', 1927 ATTORNEY been found to 'Reissued Sept.I 18, 19.28. i

- UNITED STATES- FREDERICK n.' xoLsrE'B. AND sIGUIw A. soI`.I.IE, oF sIGNons To FEDERAL TELEGRAPII COMPANY, oF

A CoRIona'rIoN 0F. CALIFORNIA.

Fano AL'ro, ca IiIFonNIA, as-V 'sAN FRANCISCO, eaLIFonNIA,

ELECTROM'AGNETIC souND nEFnoDUcEIt. 1-

origmal- No. 1,637,119, dated my 1.76,1927, serial No.1 161,824, mea 'january 1e, 1927. 'Animation nu? ressueled November 5,- 1927. Serial No. 231,373. l

This invention relates broadly to electrof magnetlc sound reproducers and more parf ticularly to-` an electromagnetic sound -reproducer which employs a free edge sound re# 5 producing diaphragm.

f One of the objects of the invention is to provide a practical construction of free edge sound reproducing diaphragm wherein mechanical vibrations may 10 cone shaped sound reproducing diaphragm where the diaphragm 1s suspended interme-` diate the apex and peripheral edge thereof.

Another object of the invention is to.pro vide an arrangement of conical shaped sound l5 reproducing diaphragm and electromagnetic driver for imparting vibrations thereto where the cone shaped 2f) center the diaphragm withrespect to the elec'- tromagnetic driver while permitting free,

1n :I y

Figure 1 is a side elevation partially in crosssection of the electromagnetic driving mechanism andthe-conical shaped sound reproduc- 35 ingrdiaphragin mounting constituting the invention; and Fig. 2 is a crossLsectional view taken on lline 22 of Fig. 1.

Heretofore inthe art vit has been'proposed to rigidly mount a conical shaped sound re- 4." .producinfg diaphragm of the cone type from its periphery and move the a spring rim at* diaphragm' bodily the principleof a havebeen ofrelatively large -size'and more 4" than nine inches velop sustained sound wavesinfunconfned from the apex. thereof o'n air. The present invention is directed to a` relatively small size lcone shapedsound ref-1 producing dia hragm in association with a 5 .driver of the e ectrodynamietype' whichhas y' andjthis winding normally be imparted to the diaphragm is supported intermediate its apex and 'peripheraledga by a iexible membrane which is arranged to` be more clearly under-l Whereporting member plunger. Such diaphragme in diameter inorder to (ley be very effective m' the '-reprol duction of the entire range of musical notes encountered in radio broadcast reception.

l The coneshaped diaphragm is free at its periphery and at the'apex thereof but is supported 'intermediate the apexand peripheral edge. An armature Winding is carried by the cone shaped sound reproducing'diaphragmv I' oats within a magnetic gap between'the p ole faces of the eleetromagnetic system. The cone iswholly supported intermediate the apex and the peripheral edge thereof so that the free edge normally iioats without a peripheral support.

Referring to the drawings in detail, reference character 1 designates the electromagnet ic driving mechanismenclosedin'a housing 2. The electromagnetic driving mechanism' 1s carried by supporting bracket 3 whichp'rotrudes from the base member 4. The-electroo magnetic driving mechanism .i's' ofthe elec-1 trodynainic typein which a magnetic-circuit is provided through the shell frame 5,6 and er 8 ,which protrudes throughv the shell closure 7 l 7, and through the magnetic pole memb forming an annular magnetic gapYQ-in- Which the cylindrical bobbin `1 0 is' arranged to'oat.

The cylindrical bobbin 'flfis secured' to the surface of the conical shaped sound reproducing diaphragm 11 intermediate the apex 12 andthe periphery 13 of the cone shaped di-" aphragm. The cylindrical bobbin 10 is flared outwardly as lrepresentedfat 14 -to conform with'theshape of the -sound reproducing diaphragm 11. The sound reproducingA diaphra 11` apex 1... and the l'free peripheral edge 13 flexible --means 15 which may extend from ythe"lsupporting member 16. The 'sup- 16 is in the form of a ringV over which a similar ring member 17 is aris suspended intermediate the^ ranged to slidefor gripping exible material such as leather therebetween. The exible material 15 maybe other sheet-like material. or -a. plurality of cordslwhich A extend beneath the outwardly ilared portion 14 of the bobbin 10. The bobbinlO and material 15 are secured inthe-form leather, rubber, linen or .of laminated layers -to the surface of the cone shaped diaphragm 11 thereby suspending the cone ,shaped diaphragm for movement with Y.

anism from aposition intermediate the apex and the free edge of the cone. The fiexible membrane or material which is stretched from the `frame members 16 and 17 provides the annular gap 9 so that it Will be noted that the air is partially, if not almost wholly confined Within the chamber.

vThe bobbin 10 carries an armature coil 19 thereon in the magnetic gap 9. Variable currents from the output circuit of an audio frequency amplification' system are passed through the conductors 20 Which connect with terminal' posts 21 on the frame of the apparatus as represented at 22. The conductors 20 are normally so small in size and light in weight that they may be glued to the surface of the Cone shaped diaphragm v11 Without impeding the'motion of the diaphragm.

A magnetic field is developed by means of lield coil 24 which is wound upon the magn'etic member 8 and supplied with power from any suitable source such as a rectifying sys-, tem which may operate from the usual alternating current lighting circuit in the home.

In order that the response curve of the reproducer may'l-be relatively flat Withoutundsired sharp resonances, We provide a metallic disc 25 adjacent the electromagnetic system `for introducing such eddy current fields as Will react vwith the normal fields of the Winding 19 produced at certain frequencies to render the operation of the apparatus'moreuniform.

Ve have illustrated theinvention as applied to a conicalshaped sound reproducing diaphragm,

but it will be understood that a flat or other shape of diaphragm may be used equall well. A

Whlle we have illustrated vour invention as applied to :1n-electromagnetic. driver of the electrodynamic type driving'a cone having a free edge,lwe may employ our invention with other types of driver driving a cone, the edge of which is'not free.

We have described our invention incertain preferred embodiments but we desire'it to be understood that l'nodiicationsmay be made and that no limitations upon our invention are intended other than are imposed by the scope ofthe appended claims.

What we claun as new and desire to secure by Letters Patent of the lUnited States i's as follows@ I A 1. An`v electromagnetic sound` reproducer `comprising electromagnetic driver, a coni- 'f cal-shaped sound reproducingl diaphragm, a

frame member. surrounding` the apex portion of s'a1d comcafshaped sound reproducing diaifexible sheet of material Sc- ',apex and cured at its edge to Said frame member and extending alono' a portion of the convex side of said conical s aped sound reproducing diaphragm in a position intermediate the apex and peripheral edge thereof for suspending said conical shaped sound reproducing diaphragmfor actuation bysaid electromagnetic ing diaphragm in a position intermediate 'theapex and free peripheral edge thereof,

and an annular.metallic plate disposed ad jacent said electromagnetic ldriver for broadening the response curve of said electromagnetic sound reproducer.

-3. An electromagnetic sound reproducer comprising an electromagnetic driving mechanism, a sound rep-roduclng diaphragm,'said sound reproducing diaphragm being connected with said electromagnetic driving mechanism, and a flexible membrane supporting said diaphragm in a vposition intermediate the apex and peripheral edge thereof, said Hexible membrane forming. a closure for an air chamber directly adjacent the sound reproducing diaphragm. y

4. An electromagnetic sound reproducer comprising an ,electrodynamic driver 'including an armature Winding and afield magnet,-

-a sound reproducing diaphragm connected ing diaphragm intermediate the apex `and free peripheral edge thereof,'said Aflexible membrane being stretched, across the front of said field magnet and forming an air chamber against which said sound repro- .ducin dia hragm is arranged to operate.

5. n e ectromagnetic sound reproducer comprising a frame structure, an electrody- ,-namic driving apparatus including a field'.

magnet and an armature winding, a conical shaped sound reproducing diaphragm arranged to carry said armature winding,`a cylindrical frame member extending from said electrodynamic driving apparatus to a position intermediate the apex and free peripheral edge of said diaphragm, anda flex-l ible` membrane stretched across said cylinreproducin -diaphragm intermediate the ree peripheral edge thereof for forming -anv air chamber ,adjacent said electrodynamic driving apparatus. 6. A sound reproducer com ldrical frame and connected with said sound rising a cone, A.an annular flexlble membgr Raving lts 1nsecured to said-cone in coritherewith., and intening of magnetic material forming an inwardly extending pole,

casing and spaced from said pole by an annu lar gap, a field winding within armature winding in said gap, 'lexible v1- bratory 'means Without the casing and associated with the armature coil to beV vibrated a core member wlthn the the casing, anl

thereby, s'nliporting means for the vibrabory 15 means frmmg therewith a substantially connecl chamber for a retarding medium between the vbratry means and e1ectromagnet', the only outlet to said chamber being through the annular ,gap which is suieintly 2 small to offer sbstantial resistance to apprelciable flow of the retardng medium therethrough'.

In testimony whereof we aix our signaf` tures..`

' FREDERICK A. KOLSTER.

A.' SOLLIE.

SIGURD 

